1. Field of the Invention
The present invention relates to a lane guidance display method, and a navigation device and a recording medium for realizing the method. More specifically, the lane guidance display method is employed by the navigation device mounted in a vehicle, for example, and used to guide the vehicle, via a display, on which lane to take to enter an intersection or exit therefrom. The recording medium contains a program for executing this method.
2. Description of the Background Art
There have been developed various navigation devices which are of a type mounted in a vehicle, for example, to guide a vehicle from a departure point to a destination or a stopover. Such a conventional navigation device displays a map covering a driving route, optionally with the heading direction indicated by voice when needed. For example, before an intersection where the vehicle is supposed to turn left, the driver hears such a voice state xe2x80x9cplease take a left turn at the next intersectionxe2x80x9d.
At an intersection on a road with several lanes, the driver may need to follow a lane control when turning right or left, or going straight. If this is the case, such guidance as xe2x80x9ctake a left turn at the next intersectionxe2x80x9d is not helpful enough for the driver to decide which lane to take. The driver has to look for traffic signs and road markings, for example, for information relating such lane control. The problem herein is, if the driver is unfamiliar with the road, he/she may often find it difficult to decide which lane to take until the last minute. The reason lies in the fact that such information relating lane control (traffic signs, and the like) is often presented in the very close vicinity of the intersection. Therefore, when the driver is unfamiliar with the road, such conventional route guidance does not provide him/her with much assistance, and consequently results in a sudden lane change or a failure in making the appropriate lane change, preventing the driver from following the searched route.
To get around such problem, the recent type of navigation device has started to guide the vehicle on the lane basis for additional guidance. For example, Japanese Patent Laid-Open Publication No. 2000-18956 discloses such a vehicle-mounted navigation device, providing lane guidance by voice for every intersection on a driving route between a departure point and a destination or a stopover in consideration of a heading direction. For example, when the vehicle is supposed to turn left at the next intersection, the driver hears a voice saying xe2x80x9cplease move into a far left lane, and keep goingxe2x80x9d before hearing xe2x80x9cplease take a left turn at the next intersectionxe2x80x9d.
Here, if the driver is unskilled in driving or unfamiliar with the area, he/she may also want to know on which lane he/she is supposed to be when exiting the intersection. That is, in a case where the vehicle needs to make turns in a row, for example first left and then right, in a short distance on roads with several lanes, the most preferred route is taking a far right lane after turning left.
In such a conventional navigation device as offering the lane guidance only when the vehicle comes in close vicinity of an intersection ahead, if the lane guidance cannot catch up with such successive turns, one mistake of wrongly exiting from a lane at the first intersection will lead to a failure in entering an appropriate lane at the next intersection. This is because the driver is more likely to miss information relating lane control when exiting from the intersection than entering. As a result, as described above, this leads to sudden lane change or a failure in making an appropriate lane change, preventing the driver from, following the searched route.
In the above conventional navigation device, lane guidance is offered by voice as appropriate together with the map of the running route on the display. The issue here is that the driver needs to correctly understand what the voice is saying (for example, distinguish between xe2x80x9cleft turnxe2x80x9d and xe2x80x9cright turnxe2x80x9d, and such lane guidance by a map display and a voice is not understandable at a glance or intuitive. Further, if the driver fails to hear the lane guidance (for example, due to loud music or the driver being on a cellular phone), the lane guidance system does not provide him/her much assistance.
Therefore, an object of the present invention is to provide a lane guidance display method for displaying a map of running route and guiding a person driving a vehicle on which lane to take at both entering an intersection and exiting therefrom, a navigation device for employing the method, and a recording medium containing a program for executing the method.
The present invention has the following features to attain the above-object.
A first aspect of the present invention is directed to a lane guidance display method for guiding, on a screen, a vehicle on which lane to take to go through an intersection. The method comprises searching for a guidance route from a departure point to a destination or a stopover based on map data including lane data, which includes a number of lanes and a lane control of roads connected to an intersection, and specifying an intersection for guidance (target intersection) located on the guidance route. The method also comprises determining, based on the guidance route and the lane data, a recommended enter lane for entering the target intersection and a recommended exit lane for exiting therefrom, and guiding the vehicle by displaying the recommended enter and exit lanes on the screen.
As described above, in the first aspect, lanes recommended respectively for entering into and exiting from a target intersection on a guidance route are determined, and then guidance is preformed. Accordingly, a vehicle can be guided with such lanes that are helpful for smooth travel, and therefore, lane guidance offered thereby is driver friendly.
Preferably, the guiding operation comprises generating an intersection image of the target intersection for lane guidance based on the lane data, generating a running path for the target intersection which passes through both the recommended enter lane and the recommended exit lane, and displaying, on the screen, a lane guidance intersection image which is a combination of the intersection image and the running path.
As such, the lanes recommended for entering into and exiting from the intersection (recommended lanes) are represented by a running path connecting the recommended lanes on an intersection image (simplified, for example) of the target intersection. Accordingly, guidance can be visually offered on a map covering the running route on a screen. Thus, a driver of the vehicle can understand at a glance how to go through the intersection by knowing which lane to take, and lane guidance is thereby driver friendly.
Also preferably, when a plurality of target intersections are in proximity, the intersection image generated in the intersection image generating operation is a combination of the target intersections in proximity, and the running path generated in the running path generating operation passes through the target intersections in proximity.
As such, by generating and displaying an intersection image which is a combination of several target intersections, even if a vehicle successively makes left and right turns in a short distance and thus, the audio guidance cannot catch up therewith, the driver can figure out at a glance how to go through the intersections based on which lane to take in advance.
Also preferably, specified as the target intersection in the specifying operation are all of the intersections found on the guidance route, and the lane guidance intersection image is displayed plurally and collectively in the displaying step in the order of the target intersections on the guidance route.
As such, the driver can grasp recommended lanes for the entire route in advance with no consideration for the distance between the actual intersections and further directions.
Here, the running path generated in the running path generating operation may be represented by one or more successive arrows directing the vehicle from the recommended enter lane to the recommended exit lane.
In this manner, the lane guidance offered thereby is driver friendly and allows the driver to understand how to go through the intersection by taking the appropriate lane, at a glance.
Further, in the determining step, additionally calculated for each exit lane may be a lane level of recommendation, which is represented by discrete or successive numbers, and the running path generated in the running path generating operation may be represented in various manners, depending on the lane level of recommendation, by one or more successive arrows directed from the recommended enter lane to the recommended exit lane.
In this manner, the running path can be represented by such successive arrows in various manners depending on the lane level of recommendation. This leaves lane selection to the driver discretion by showing him/her the level of recommendation for each exit lane, and in this sense, the lane guidance offered thereby is driver friendly.
Still further, in the determining operation, grounds for the recommended enter and exit lanes may be additionally found, and in the displaying operation, an image based on the grounds may be displayed together with the lane guidance intersection image.
In this manner, together with the running path represented by such successive arrows, the driver can see the grounds for the lane recommendation, therefore can rest assured in addition to the effects achieved in the foregoing.
A second aspect of the present invention is directed to a navigation device for guiding a vehicle on a screen from a departure point to a destination or a stopover. The device comprises a map data storage part for storing map data including lane data, which includes the number of lanes and lane control of roads to be connected to an intersection, a route search part for searching for, based on the map data, a guidance route from the departure point to the destination or the stopover, a vehicle position detection part for detecting a vehicle position on the map data, and a target intersection operation part for searching for and specifying, based on the guidance route and the map data, an intersection requiring guidance on the guidance route (target intersection). The device also comprises a recommended lane operation part for determining, based on the guidance route, the lane data, and the target intersection, a recommended enter lane and a recommended exit lane for the target intersection, a guidance part for generating, based on the recommended enter and exit lanes and the lane data, lane guidance data required for display on the screen, and an output part for displaying guidance on the screen according to the lane guidance data.
Preferably, as the lane guidance data, the guidance part generates an intersection image for lane guidance based on the lane data for the target intersection, generates a running path which passes through the recommended enter lane and the recommended exit lane for the target intersection, and generates a lane guidance intersection image which is a combination of the intersection image and the running path.
Also preferably, when a plurality of target intersections are in, the intersection image generated by the guidance part is a combination of the target intersections in proximity, and the running path generated thereby passes through the target intersections in proximity.
Also preferably, the target intersection operation part specifies all of the intersections found on the guidance route as the target intersections, and the guidance part outputs the lane guidance data to the output part to plurally and collectively display the lane guidance intersection image in order of the target intersections on the guidance route.
Here, the running path generated by the guidance part may be represented by one or more successive arrows directing the vehicle from the recommended enter lane to the recommended exit lane.
Further, additionally calculated by the recommended lane operation part may be a lane level of recommendation for each exit lane represented by discrete or successive numbers, and the running path generated by the guidance part may be represented, in various manners depending on the lane level of recommendation, by one or more successive arrows directed from the recommended enter lane to the recommended exit lane.
Still further, the recommended lane operation part may additionally find grounds for the recommended enter and exit lanes, and the guidance part may output the lane guidance data to the output part to display an image based on the grounds together with the lane guidance intersection image.
As the second aspect, a navigation device is so structured as to execute the lane guidance display method of the above first aspect, thereby performing the effective lane guidance of the present invention.
A third aspect of the present invention is directed to a recording medium on which a lane guidance display method for guiding, on a screen, a vehicle on which lane to take to go through an intersection is recorded as a program executable on a computer. The program at least carries out searching for a guidance route from a departure point to a destination or a stopover based on map data including lane data, including the number of lanes and lane control of roads to be connected to an intersection, specifying an intersection for guidance (hereinafter, refers to as a target intersection) located on the guidance route, determining, based on the guidance route and the lane data, a recommended enter lane for entering into the target intersection and a recommended exit lane for exiting therefrom, and generating an intersection image of the target intersection for lane guidance based on the lane data. The program also carries out generating a running path for the target intersection which passes through both the recommended enter lane and the recommended exit lane, and displaying, on the screen, a lane guidance intersection image which is a combination of the intersection image and the running path.
Here, the running path generated in the running path generating operation may be represented by one or more successive arrows directing from the recommended enter lane to the recommended exit lane.
Further, in the determining operation, additionally calculated for each exit lane may be a lane level of recommendation, which is represented by discrete or successive numbers, and the running path generated in the running path generating operation may be represented, in various manners depending on the lane level of recommendation, by one or more successive arrows directed from the recommended enter lane to the recommended exit lane.
Still further, in the determining operation, grounds for the recommended enter and exit lanes may be additionally found, and in the displaying operation, an image based on the grounds may be displayed together with the lane guidance intersection image.
As is the third aspect, a program carrying out the lane guidance display method of the first aspect is recorded on a medium, whereby the method can be supplied to an existing device in the form of software.